'An accident, mishap, or, more archaically, misadventure, is an unforeseen and unplanned event or circumstance, often with lack of intention or necessity. It usually implies a generally negative outcome which may have been avoided or prevented had circumstances leading up to the accident been recognized, and acted upon, prior to its occurrence.'
Splitting hairs, but in my book, carrying a sidearm involves the possibility that, if CARE is not exercised, could discharge. Carelessness is negligence in my book. Firearms do not generally discharge without assistance from a human. Therefore, three classes of discharge can exist- negligent (carelessness of a human), intentional, and accidental, wherein a mechanical malfunction of the firearm causes it to discharge without the help of a human. Accidental discharges are VERY rare, except for Remingtons; but that's another story.